MIND WHAT YOU EAT

Battling weight gain, low mood or tiredness? Highly processed foods could be to blame for making us feel this way, as nutritionist Anita Bean discovers

The effect on our bodies of eating too many ultra-processed foods

We all know about avoiding foods that give a short-term mental boost but no nutritional gain, but now modern imaging techniques are showing that eating a great deal of ‘ultra-processed food’ actually alters the neural connections in our brains. In the BBC documentary What Are We Feeding Our Kids?, Dr Chris van Tulleken investigated what effect eating a diet made up of 80% ultra-processed foods for four weeks would have on his brain and body. The findings were shocking, and he reported weight gain, health problems and food cravings.

Even more worryingly, one in five people in the UK already eats this way. Ultra-processed foods currently account for more than half (57%) of all our calories, according to a study reported in The British Medical Journal. In children that figure rises to 64% of their diets and in adolescents it is 67%. Doctors suspect it is these foods that are causing a spike in obesity among youngsters.

The foods we are talking about include products such as crisps, biscuits, fizzy drinks, cakes, ready meals and mass-produced bread. They also include products that are marketed as healthy, such as cereal bars, vegan meat substitutes and plant milks. ‘In essence, they are foods formulated through industrial processes that are combined with additional ingredients, such as sweeteners, colouring, stabilisers and preservatives, and go through multiple processes,’ explains registered dietitian Ro Huntriss. ‘When looking at an ingredients list, if the majority are things that you would not use when cooking at home, the product is likely to be classed as ultra-processed.’

The ultra-processed problem

Many experts think we’re eating far too many ultra-processed foods and, when eaten in large amounts, these are linked to a number of health conditions and problems. As well as obesity, French researchers found that a 10% increase in the amount of ultra-processed foods in our diets was linked to a 12% increase in cancers. Meanwhile, a study of nearly 20,000 people between 1999 and 2014 found that eating more than four servings of these foods daily was linked to a 62% increased risk of early death. Experts are so worried about the obesity epidemic they believe is being caused by ultra-processed foods that Brazil has banned the advertising of them, while France and Canada officially recommend limiting their consumption.

Testing the theory

At the end of the BBC experiment, Dr Chris gained almost 7kg and moved from a healthy weight to overweight. He reported poor sleep, heartburn, low mood, anxiety, sluggishness and low libido. He also had piles due to constipation. Researchers at University College London looked at his brain using state-of-the-art scanning (MRI) at the beginning of the experiment and then at the end. They found that areas of Chris’s brain responsible for feelings of reward linked up with areas that drive repetitive behaviour – a similar response to using substances such as cigarettes, drugs and alcohol. Previous studies have found that ultra-processed foods can trigger addictive-like eating behaviours. Indeed, Chris found himself craving these types of foods much more often.

What makes these foods so hard to resist?

Ultra-processed foods are made to be tasty and make us want to eat more. This is down to what the food industry calls hyper-palatability, or ‘deliciousness’. One tactic that food manufacturers use is called the ‘bliss point’, and involves combining fat, sugar and salt in just the right ratios, so the food becomes almost

impossible to stop consuming. Think chocolate, ice cream, crisps and biscuits – their perfect balance of sweet and salty, fatty and salty, fatty and sweet, or all three, get the brain’s reward centres buzzing. You get a dopamine hit that triggers endorphins and other chemicals, which gives you a moment of bliss. And when that moment comes to an end, your brain wants more. A brain-imaging study showed the more people experienced reward from eating ice cream, the more they needed to consume to get the same enjoyment. Hardly surprising then that people who eat large quantities of ultra-processed foods are more likely to gain weight.

Why do they cause weight gain?

Scientists don’t know for sure what it is about ultra-processed foods that causes weight gain. But it’s most likely a combination of their nutrient make-up and the physical act of processing. Ultra-processed foods have a high ‘calorie-density’, meaning they contain lots of calories per gram and are high in sugar, salt or saturated fat. They are typically low in fibre and protein, all of which makes them less filling, easier to overeat and less likely to satisfy the appetite than unprocessed or whole foods.

But the impact of ultra-processed products goes beyond their nutritional composition. ‘When food is processed, the body will absorb more of the calories it contains,’ explains Giles Yeo, a geneticist at the University of Cambridge and author of Why Calories Don’t Count. ‘Processing increases a food’s “caloric availability”, the amount of calories the body can actually absorb as opposed to the number of calories locked up in the food. It makes a food more digestible.’

For example, if you consume 100 calories of sweetcorn, only a fraction is absorbed because much of the caloric content is bound up in fibre, which we cannot digest. But when it’s processed to make cornflakes or tortillas, a much larger fraction of calories becomes available to the body. In other words, your body takes more calories from a processed food than it would do from the same food in its unprocessed state.

In one ground-breaking study, researchers at the US National Institutes of Health compared two diets containing the same calories, fat, sugar, fibre and salt, but one was made up mostly of unprocessed foods and the other mostly of ultra-processed foods. The participants spent two weeks on each diet and were told to eat as much as they liked. On the ultra-processed diet, the volunteers ate an extra 500 calories per day and put on a kilo of weight over two weeks. When they ate unprocessed foods, they lost weight.

One possible explanation is that ultra-processed foods were consumed more quickly because they’re softer and easier to chew and swallow, which potentially resulted in delayed signals of fullness. Previous studies prove that eating slowly decreases hunger. Blood tests showed that the hormones responsible for hunger increased on the ultra-processed diet, which may explain why participants ate more. The effect of additives such as artificial sweeteners on the gut microbiome is another theory.